SCEA/OCMJEA Assignment

This post has been moved to http://srinichekuri.com/2013/06/04/sceaocmjea-assignment/

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Today I got the magical email that I have passed assignment with a score of 146/160. Needless to say, I was very happy. I am blogging my experience with the hope that future aspirants will benefit from this.

I have submitted Assignment about 10 days before voucher expires.To start I have downloaded the assignment almost immediately after my Step-1 which started my clock(for people who don’t know Step 2 and Step 3 should be done within six months after the assignment is downloaded). Well if the question is did it actually take six month to complete this project, the answer is a big NO. I have started working on it for few hours everyday for 2 weeks. When I understood the assignment well and designed the system, I also drew class diagrams, sequence diagrams on scrap papers and then I stopped. I guess I was thinking that the challenging part is complete and I had to take care of the boring part( documenting it).
When I took up the project again after 5 months, I realized that it was a mistake due to following reasons:

  • The break wiped out project from my memory and I had to start all over again. Ofcourse my design that I scrapped on paper really helped me to get it all back.
  • I have under estimated deployment diagram. I never had to decide on hardware profile before and this turned out to be quite challenging.
  • UML took good chunk of time. By UML I mean deciding on the tool, planning on how you project your diagrams to make evaluation easy and actually drawing them took some time.
  • Documenting did take some time.

The project that was assigned to me was a web application with peak usage of 200 users. The domain diagram had 11 classes.
I have worked on UML diagrams in following order:
Class Diagram:
I have decided to divide my class diagrams into 2 parts by separating out domain classes. Although I started out with a thought to accommodate all the classes into one diagram, I thought that domain classes can be shown separately just to avoid clutter. This worked out pretty well for me. I have used various patterns like MVC, Factory, Business Delegate, Proxy Pattern, Data Access Object, Value Object, Transfer Object and Domain store. I have used following technologies/frameworks:

  •     Struts 2.0 for presentation layer.
  •     EJB 3.0 enterprise beans for session and transaction management.
  •     JPA for persistence.
  •     Java Mail API for email notification.
  •     Spring 3.0 for Authentication and Authorization.
  •     Spring 3.0 for dependency injection, aspect-oriented programming.
  •     Log4j for logging.
  •     WebServices.
  •     Ehcache for Caching (Out of box with Spring 3.0).

My class diagram also included few classes and jsps for user scenarios that were not mentioned in the requirement. For Eg: Maintenance module was not mentioned in my assignment, I have included that after adding proper assumptions.
In all I had 9 jsps, 25 classes and 11 domain objects.
Although I mentioned class names for value objects and transfer Objects, I didn’t show them in my class diagram.

Sequence Diagram:
I had six sequence diagrams in my project. I made sure all the use cases that are mentioned in assignment are addressed here. I had to do some reading for this as I found that UML 2 had good features to represent our views. I have used two opts.

Component Diagram:
I have done this after I was almost done with class diagram and know what to be done in sequence diagrams. This helped me with all the components that would go under various tiers.

Deployment Diagram:
This was a very good learning experience in whole of the project. Having worked for multinational companies all through my career, I never go to involve myself in hardware discussions. I did however have experience working on a projects where I had to make decisions on over all architecture (Firewalls, load balancer, server clustering, hot backups etc). This was the strategy that I have followed before deciding on the hardware profile and the vendor that would host my application

  • In-house hosting costs vs Outsourcing hosting costs
  • Privacy compromises for in-house vs outsourcing.
  • Licensing costs
  • Resource costs for maintenance

For my project, privacy was not a concern (added this to assumption as well) and the cost of hosting in house by buying a server was too high (Eg: Cost of IBM Power 710 Server, 4 core 4.2 Ghz with 8GB RAM, Rack mount 2 x 146 GB SFF Harddisk (IBM AIX 5.3 operating system) is $6255 without other licensing costs and resource costs). I have decided to outsource hosting for my application. The advantage in my case for outsourcing was that maintenance costs(possibly licensing costs) were included in hosting costs.

For Outsourcing I have looked at two options

  • Rent Physical Server: I have looked into multiple providers but the cheapest option was provided by rackspace.com. It costs $262.80/month for box with 4GB RAM, 2 core 160 GB disk space (Linux operating system)
  • Cloud Solution: Again there were multiple that provided cloud solutions but I best I found was Amazon Elastic Compute Cloud (Amazon EC2) service. The price for ‘3 year upfront option’ for ‘M1 Large Instance’ $384.

I have decided to go for Amazon Ec2 as it had other advantages.

Amazon Elastic Compute Cloud (Amazon EC2) services seem to be secure, reliable and have scalability options for increased traffic in future.

  • Load Balancing: This service provides elastic load balancing which automatically distributes incoming application traffic across multiple Amazon EC2 instances. This has capability to detect unhealthy instances within a pool and automatically reroute traffic to healthy instances.
  • Hardware/Software Application Server – Primary: I chose ‘M1 Large Instance’ option which provides 7.5 GB of memory, 4 EC2 Compute units (2 Virtual cores with 2 EC2 compute units each, 850 GB of disk space, 64-bit platform). Operating System is Red Hat Enterprise Linux. Application Server is IBM Websphere.
  • Application Server – Backup:  I chose ‘M1 Medium Instance’ option which provides 3.75 GB of memory, 2 EC2 Compute Units (1 Virtual core with 2 EC2 Compute units each, 410 GB of disk space, 64 bit platform). Operating System is Red Hat Enterprise Linux. Application Server is IBM Websphere.
  • Database (Primary/Backup): The package selected above comes with local installation of database. Following were chosen for this application:
    • Microsoft SQL Server-Standard
    • Windows 2008 R2 6.1 (Operating System)
  • Scalability: Amazon EC2 services provide auto scaling which scales up automatically to maintain performance in case of spikes.
  • Pricing:
    • Application Server+Database(primary) – 3 year upfront option for $384 (Amazon EC2 offers various options but this is the cheapest)
    • Application Server+Database(Backup) – 3 year upfront option for $192
    • Projected operating budget for hardware/software for 3 years = $384 + $192= $576

Assumptions:
I had about 10 assumptions. I have put all assumptions that effected my design/hardware/software decisions.

Risks and Mitigation Plan:
I had about 12-15 risks and mitigations strategies listed. I have sorted the risks in the order of their importance so that the top risk is shown at the top.

Documentation:
I have provided some extensive write-up for each section. I wanted to make sure that all my thoughts were put in there as my main motto was to make sure that evaluator understands everything that I had in mind. A lot of documentation was done as I was doing UML diagrams to diversify my work.

Creating Jar file:
I have zipped all my files and changed the extension to .jar. (We can as well create a jar from command prompt – google it).

SCEA blogs:

Reference Material:

Questions I had and how I addressed them:

  • How detail should class diagram be?
    Pretty detail, but make sure that details like patterns, methods, method parameters are visible. I advice to not include any classes that would add clutter (DTO, Transfer objects, Value Objects etc.). Don’t compromise on quality of class diagram for other factors like restricting class diagram to one page.
  • Do I have to show jsps in class diagram?
    Yes.
  • Should I show DTO/Transfer Objects/Value Objects ?
    You have to decide if this makes any sense to show them. I didn’t show any DTO, Transfer Objects and Value Objects. I just mentioned them as parameters in methods and I did mention them in my write up for class diagram.
  • Should getter/setter methods in a class be shown?
    No.
  • What tool did I use for UML diagrams?
    MS Visio 2010
  • What format of images did I use for UML diagrams?
    I have converted all my UML diagrams to PNG format. I found this format to be more compact in size without any compromise in quality.
  • How did I convert UML diagrams to images?
    I have used SnagIt. SnagIt has settings to capture a scrolling page and later I have cut the unwanted area and saved the image in PNG format.

My other posts related to SCEA: SCEA/OCMJEA Experience (Step-1), SCEA/OCMJEA Essay

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SCEA/OCMJEA Experience (Step 1)

This post has been moved to http://srinichekuri.com/2012/11/30/scea-experience-step-1/

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Few days back I got through SCEA Step-1 with 82%. I wanted to blog my experience for those who are taking this exam and looking for advice.

I have first thought of taking this exam more than a year ago. I have started preparing for this exam about the same time. Also I took a course for SCEA offered through WhizLabs. First thing, I should say is if you have experience working on Java/J2ee technologies you don’t have to take any course. The course that I took didn’t offer me much help expect to let me know that I will have to read before I take this exam. The exam requirements changed after I took this training (now Oracle wants us to take a course before getting certified).

Anyways when I made up my mind to take this exam again couple of months back, I started off with a blank mind researching on how should I get started. After some research I had a plan of action:

Below is detailed description of the preparation for various sections that needs to be prepared:

Section 1: Application Design Concepts and Principles
Mikalai Zaikin’s SCEA Notes
I knew about design concepts but there were few things that I picked up from these notes. Anyways I felt that his notes should be good enough for people who are preparing for exam. Let me caution you that you should understand this chapter in detail as the concepts in this chapter form a base for lot of design questions for exam.

Section 2: Common Architectures
Mikalai Zaikin’s SCEA Notes

Section 3: Integration and Messaging
Adel Almoshaigah SCEA Notes
I made my notes based on Adel’s notes. I had good enough knowledge on Messaging but had to understand JCA in detail and I felt that his notes gave idepth information on JCA.

Section 4: Business Tier Technologies
Adel Almoshaigah SCEA Notes
I made my notes based on Adel’s notes. I knew pretty much all the information in this topic due my experience as developer on this topic. I read EJB3 in Action book to know more details about EJB3. I didn’t go in depth into programming while reading this book.

Section 5: Web Tier Technologies
Adel Almoshaigah SCEA Notes
I made my notes based on Adel’s notes. I knew pretty much all the information in this topic due my experience as developer on this topic.

Section 6: Applicability of Java EE Technology
Adel Almoshaigah SCEA Notes

Section 7: Patterns
Mikalai Zaikin’s SCEA Notes
Core J2EE Patterns
Design Patterns

Mikalai Zaikin notes is based on the prescriped books. There were few patterns that I knew out right from my experience but there we few that were completely new to me and there were few that confused me as they looked the same to me. That’s where books played a big role. Books have a very detailed description on the patterns and when and where they are used. I have made my own notes that made me understand the patterns better.

Section 8: Security
Mikalai Zaikin’s SCEA Notes.

Notes cover all the needed information in detail. Although I knew about few topics in bits and pieces, this section was completely new to me. I had to go through this chapter multiple times to understand few things.

Dos:
Make your own notes for each topic so that you can concentrate more on topics that you are not good yet.
Understand the concept enough to be able to apply the concept in various scenarios.
Train yourself to understand the question enough to choose the right answer. (The gramnmer used in exam is confusing lot of times). I can’t stress on this point enough because there are lot of questions in exams where you need to read and should be able to filter out unnecessary information and make a decision by processing the right information.

Don’ts:
Don’t memorize any concepts because it will only lead to more confusion
Don’t expect exam to use any words/phrases from the prescriped books
Don’t always concentrate on exam objectives, read to gain knowledge. This will help to crack design questions in exam easily and you will be prepared psychologically for any questions that might surprise you in exam.

For practice I bought practice questions from test king. I have bought practice questions from test king for all my certifications and they have never disappointed me. I would recommend test king for SCEA too, it had 300 odd questions for practice and I have done some 250 for practice and they helped me a lot. Practice questions till you are very comfortable with the pace at which you read, able to understand the questions at ease and are able to get reasonable amount of questions correct.

Exam Experience:
I have taken my test in Pearson test center. I reached there 30 minutes early and I was allowed to take the test 15 minutes before my scheduled time. After taking many certifications I trained myself to give equal importance to all the questions and I would suggest everyone to follow the same. When ever I stumbled on some question, I would just give it my best shot, mark the question (if you have taken certification tests earlier, you would know about this feature. You can mark a question for review later) and move on. I was able to complete the test in about 90 minutes. Then I went back to my marked questions, gave them a second thought. I clicked on finish button about 10 min before finishing mark.

My other posts related to SCEA: SCEA/OCMJEA Assignment, SCEA/OCMJEA Essay

Hope this information will help you and all the best for aspirants of SCEA.
thanks,
-Srini.